The rationale for experiments proposed in this application begins with the observation that the mRNA of a Drosophila material effect gene, bicoid, is localized at the anterior end of oocytes and early embryos. Further, two other maternal effect genes, swallow and exuperantia, are necessary for this localization. I propose to determine the function of the swallow gene in this process, and parameters of the bicoid message localization process itself. The localization of determinants in animal eggs is of widespread occurrence, and information gained with respect to the function of the swallow gene in Drosophila should be of fundamental importance in understanding developmental processes. This application includes the following experiments: (1) We will determine the significance of an unusual feature of the swallow gene region, the presence of two long direct repeats. We would like to know whether one or both repeats encode swallow function. (2) We will determine the time of synthesis and persistence of the swallow protein, and its location in the egg chamber and embryo at gross and subcellular levels. We will look at swallow protein distribution in oocytes and embryos from wildtype, swallow- and exuperantia- mothers. (3) We will examine the organization of the cytoskeleton in swallow- egg chambers and embryos, testing aspects of the idea that the swallow+ gene product has a role in cytoskeletal organization. (4) We will determine the effects of inhibitors of cytoskeletal organization on the localization of bicoid mRNA and swallow protein. (5) We will characterize the molecular associations of swallow protein and bicoid message in Drosophila oocytes and embryos by fractionation, immunoprecipitation and in vitro binding experiments.